Stephen Sillett

When I was a kid, I was inspired by forests in the Appalachian Mountains of south-central Pennsylvania, where we frequently hiked, watched birds, caught reptiles and amphibians, and climbed trees. I always wanted to be a scientist.

How did you get started in your field of work?

At Reed College in Portland, Oregon, friends and I frequently climbed trees on campus to help alleviate the stress of coursework. During a break from classes in 1987, three of us drove south to see California redwoods for the first time. Deep in the forest, I found a tall tree near the coast that could be climbed from the ground without any equipment, though in hindsight this was very risky and foolish. That treetop view of lush old-growth forest beneath an ocean horizon made me realize I wanted to devote my career to exploring forest canopies.

What inspires you to dedicate your life to forests?

Tall forests are my favorite places on Earth. I am inspired by the hidden beauty and amazing phenomena occurring within and on the surfaces of giant trees far above the ground. Like us, a tree begins life as an embryo, but it must stay rooted in place. Despite this obvious handicap, a tree can live more than 1,000 years, become over 300 feet tall, and produce more than 300 tons of wood. Even in old age, a giant tree still makes, on average, more wood annually than earlier in its life when it was smaller. While living for its own sake, a giant tree's crown also supports incredible biodiversity, including epiphytic lichens, mosses, ferns, flowering plants, and arboreal soils crawling with insects, spiders, mites, crustaceans, mollusks, and even salamanders.

What's a normal day like for you?

When I am not teaching, a normal day for me begins soon after dawn as my research team hikes to the forest to begin measuring trees. We ascend ropes into tree crowns, working in teams to map structures, install equipment, or collect samples. Often we are aloft for eight hours or more per day. Some of the gnarliest trees require many days of climbing to complete measurements. Not all days are spent climbing, because a roughly equal number of days are devoted to work in the laboratory processing samples, analyzing data, or writing.

Do you have a hero?

My heroes are those, like Albert Einstein, who work like it is play and apply their skills to increase human understanding of nature.

What has been your favorite experience in the field? The most challenging?

Working with a National Geographic Society team led by photographer Michael Nichols in February 2011, I helped climb and install equipment to document the greatest tree in all the mountains of the world, a 3,200-year-old giant sequoia I first saw (and wanted to climb) in 1987. This was an unusually heavy snow year in the Sierra Nevada, so there were already many feet of snow on the ground and more snow falling such that the tree's largest limbs were covered with several feet of snow. Moving through the frozen crown of this colossal tree required great care so as not to dislodge any snow, because documentation of the tree in full winter glory was Nichols' primary objective. One of my chief tasks was to deploy an access rope on the farthest edge of the crown near the tip of the tree's largest limb, over 60 feet away from the main trunk. The journey to this position, the view from there looking back on the mighty tree and its neighbors, and then rappelling 200 feet down from the limb into deep snow on the ground I will never forget.

What are your other passions?

These I keep to myself.

What do you do in your free time?

When I am not climbing trees, working the laboratory, or teaching, I am usually hiking, gardening, or traveling.